An HTTP 403 "Forbidden" error means that the server to which you've sent your request is refusing to let you access that URL, perhaps because it's not open to the public, or requires extra authentication.
If I try the URL https://s3-us-west-1.amazonaws.com/fasttext-vectors/wiki.en.vec from a web-browser, I get the same error. So this isn't really an issue with your code, or python, or pytorch, or fasttext. You've just got an improper expectation that the given URL will return what you wnat it to.
What reference, or entity, made you think https://s3-us-west-1.amazonaws.com/fasttext-vectors/wiki.en.vec would give you what you need? You may need to follow-up with whoever recommended that URL, and let them know their recommendation does not work, or find an alternate source.
Only if an URL works for you in your browser should you expect it will also work in your code, with no extra authentication steps. And, it still might break for other reasons, like the system where your code is running having a disfavored network IP-address – so before supplying such an URL to configure a custom subclass of Vectors, you might run some code from that same system to verify the URL loads at all.